The present invention relates to a method for producing stereoscopic photographs, and particularly to a method wherein a stereoscopic photograph is produced by exposing a lenticular screen and photosensitive film to an object field through a wide effective aperture.
A well known method for producing stereoscopic or three dimensional photographs is described in U.S. Pat. No. 3,503,316 to Takano et al. In accordance with the known technique, a camera is provided with a photosensitive film and a cylindrical lenticular screen adjacent to the film. The lenticular screen is shifted in position by one lenticule as the film is exposed to an object field through a variety of aspect angles. The variation in exposure to the object field is usually produced by the use of a narrow aperture which is moved with respect to the object field in a direction which is transverse to the optical axis of the camera lens and transverse to the lenticules of the lenticular screen. The moving narrow aperture may be achieved by movement of the camera as indicated in the Takano specification, or may be effected by moving of a narrow aperture slot across a wide aperture lens as shown in U.S. Pat. No. 3,521,947 to Jones. In either case, in accordance with the understanding of the prior art, it was considered necessary that the effective aperture, that is, the total distance through which the aperture is moved during the exposure of the film, had to equal and preferably exceed the human interocular distance of approximately 65 mm.
Another technique for producing stereoscopic photographs makes use of a camera with a large diameter lens of the type described in U.S. Pat. No. 2,562,077 to Winnek. In a camera of this type, the film is fixed with respect to the lenticular screen and is simultaneously exposed to the object field from a variety of angles through the large diameter lens. As shown in U.S. Pat. No. 3,683,773 to Dudley, this type of camera may use a spherical lenticular screen as well as the more customary cylindrical screen. In accordance with the understanding of the prior art, such large diameter lens cameras also were provided with effective apertures which equaled or exceeded the human interocular distance of 65 mm.
Heretofore, however, such prior art wide aperture techniques have been found to produce unsatisfactory results. Poor image quality results from the foregoing techniques because the images of objects which are nearer to or further from the camera than the focused distance tend to be defocused on the image plane and consequently spread out over a large area. This spreading of the image is directly proportional to the size of the effective aperture of the camera, that is, the large aperture size or the distance over which a small aperture opening is moved during the exposure process. When excessive image spreading takes place in the camera, as frequently occurs where the effective aperture is 65 mm or greater, the images of objects in the stereoscopic photograph may appear blurred or faded to the extent that images of some objects appear to lack solidity.
The method of the present invention overcomes these and other limitations of prior art stereoscopic photographic techniques.